Species diversity of longicorn beetles in humid warm-temperate forests: the impact of forest management practices on old-growth forest species in southwestern Japan

摘要

In the humid warm-temperate zone of southwestern Japan, old-growth forests have been seriously fragmented to small remnants due to traditional agriculture and coppicing as well as recent rapid plantation with conifers. Assemblages of longicorn beetles (Coleoptera: Disteniidae and Cerambycidae) were compared among old-growth forests, second-growth forests and conifer plantations using collision traps baited with chemical attractants. Species richness of longicorn beetles was poorer in second-growth forests and conifer plantations than in old-growth forests. It was proved by multidimensional scaling (MDS) that the beetle assemblages of old-growth forests were distinct from those of conifer plantations, while those of second-growth forests were intermediate between them. Further analysis showed that a number of species, including many Pidonia spp., were specific to or closely associated with old-growth forests, and the results were largely supported by the indicator value (IndVal) approach. It is likely that many of such old-growth forest species in the larval and pupal stages require large broad-leaved trees standing or fallen with thick bark. At the same time, the flower-visiting adults would play an important role in pollinating various herbaceous and woody plants. Regional forest management for the conservation of insect biodiversity is also discussed.